This project is focused on functional studies of NK receptor and T cell receptor recognition. Our approaches include: 1) the development and characterization of mouse strains transgenic for pathogenic T cell receptors--the animals develop autoimmune gastritis, a model for pernicious anemia; and 2) the development of a general system for identifying ligands to NK and T cell receptors that have physiological function. With respect to the first project, we have cloned and expressed two different TCR from T cell clones that show specificity for two peptides from the gastric H/K ATPase. One of these clones causes a Th1 type disease, and the other a Th2 disease. The Th2 disease is characterized by eosinophilic and polymorphonuclear leukocyte infiltrates in the gastric mucosa. Transgenic animals expressing the TCR from each of these clones have been produced and have been analyzed. The transgenic derived from the Th1 clone, TXA23, develops a fulminant autoimmune gastritis within 10 days of birth. The transgenic derived from the Th2 clone, TXA51, has a less fulminant disease. This second model offers to provide insight into how inflammatory (Th1) cytokines influence autoimmune disease in a manner distinct from Th2 cytokines. Cells taken from the Th2 diseased animals can be maintained in vitro as Th2 cells, or if stimulated with progressive doses of antigenic peptide presented by dendritic cells, can differentiate into Th1 cells. Detailed studies of the pathophysiology of the disease process are in progress. With respect to the second project, we are developing functional indicator cells that allow the identification of ligands for known, cloned receptors. Advances include:1) the development of a useful whole animal model for organ specific autoimmunity in our animals that are transgenic for the ATPase reactive TCR--these animals develop a fulminant autoimmune disease completely spontaneously without priming with antigen; 2) the demonstration that a Th2 disease, considerably milder in phenotype has developed in an animal that has a different TCR receptor; 3) the demonstration that the Th1 or Th2 phenotype of the disease causing cells can be changed by changing the antigen density of antigen presenting cells. We have recently made considerable progress in: 1) fine structure mapping of the epitopic residues of the H/K ATPase as seen by the MHC-II IA-d restricting element; and 2) developing MHC-II tetramers of IA-d that can be loaded with the epitopic peptides to use as crucial reagents in stimulating and visualizing the autoreactive T cells in these autoimmune animals.